A fully microrealistic, propensity version of quantumtheory is proposed, according to which fundamental physical entities - neither particles nor fields - have physical characteristics which determine probabilistically how they interact with one another . The version of quantum "smearon" theory proposed here does not modify the equations of orthodox quantumtheory: rather, it gives a radically new interpretation to these equations. It is argued that there are strong general reasons for (...) preferring quantum "smearon" theory to orthodox quantumtheory; the proposed change in physical interpretation leads quantum "smearon" theory to make experimental predictions subtly different from those of orthodox quantumtheory. Some possible crucial experiments are considered. (shrink)

This paper investigates the possibiity of developing a fully microrealistic version of elementary quantum mechanics. I argue that it is highly desirable to develop such a version of quantum mechanics, and that the failure of all current versions and interpretations of quantum mechanics to constitute microrealistic theories is at the root of many of the interpretative problems associated with quantum mechanics, in particular the problem of measurement. I put forward a (...) propensity microrealistic version of quantum mechanics, and suggest how it might be possible to discriminate, on expermental grounds, between this theory and other versions of quantum mechanics. (shrink)

In this paper, possible objections to the propensity microrealistic version of quantum mechanics proposed in Part I are answered. This version of quantum mechanics is compared with the statistical, particle microrealistic viewpoint, and a crucial experiment is proposed designed to distinguish between these to microrealistic versions of quantum mechanics.

In this paper I put forward a new microrealistic, fundamentally probabilistic, propensiton version of quantumtheory. According to this theory, the entities of the quantum domain - electrons, photons, atoms - are neither particles nor fields, but a new kind of fundamentally probabilistic entity, the propensiton - entities which interact with one another probabilistically. This version of quantumtheory leaves the Schroedinger equation unchanged, but reinterprets it to specify how propensitons evolve (...) when no probabilistic transitions occur. Probabilisitic transitions occur when new "particles" are created as a result of inelastic interactions. All measurements are just special cases of this. This propensiton version of quantumtheory, I argue, solves the wave/particle dilemma, is free of conceptual problems that plague orthodox quantumtheory, recovers all the empirical success of orthodox quantumtheory, and at the same time yields as yet untested predictions that differ from those of orthodox quantumtheory. (shrink)

Typically, human decision making is emotionally and does not conform to classical probability (CP) theory. As quantum probability (QP) theory emphasises order, context, superimposition states, and nonlinear dynamic effects, one of its major strengths may be its power to unify formal modeling and realistic psychological theory (e.g., information uncertainty, anxiety, and indecision, as seen in the Prisoner's Dilemma).

Quantum probability (QP) theory can be seen as a type of vector symbolic architecture (VSA): mental states are vectors storing structured information and manipulated using algebraic operations. Furthermore, the operations needed by QP match those in other VSAs. This allows existing biologically realistic neural models to be adapted to provide a mechanistic explanation of the cognitive phenomena described in the target article by Pothos & Busemeyer (P&B).

The interpretation of quantum mechanics is discussed from the viewpoint of quantum logic (QL). QL is understood to concern the possible properties that can be ascribed to a physical system SYS. The micro-state of SYS at any given moment t is identified with the set of all properties actualized by SYS at time t. Minimal adequacy requirements are proposed for all interpretations of micro-states. A strict interpretation is defined to be one according to which the properties (...) ascribable to SYS are individuated by the projection operators on the associated Hilbert space. Two strict interpretations are examined. Kochen's interpretation is also discussed, and it is argued that it is not a strict interpretation. (shrink)

In this new edition, Arthur Fine looks at Einstein's philosophy of science and develops his own views on realism. A new Afterword discusses the reaction to Fine's own theory. "What really led Einstein . . . to renounce the new quantum order? For those interested in this question, this book is compulsory reading."--Harvey R. Brown, American Journal of Physics "Fine has successfully combined a historical account of Einstein's philosophical views on quantum mechanics and a discussion of some (...) of the philosophical problems associated with the interpretation of quantumtheory with a discussion of some of the contemporary questions concerning realism and antirealism. . . . Clear, thoughtful, [and] well-written."--Allan Franklin, Annals of Science "Attempts, from Einstein's published works and unpublished correspondence, to piece together a coherent picture of 'Einstein realism.' Especially illuminating are the letters between Einstein and fellow realist Schrodinger, as the latter was composing his famous 'Schrodinger-Cat' paper."--Nick Herbert, New Scientist "Beautifully clear. . . . Fine's analysis is penetrating, his own results original and important. . . . The book is a splendid combination of new ways to think about quantum mechanics, about realism, and about Einstein's views of both."--Nancy Cartwright, Isis. (shrink)

It is usually taken for granted that orthodox quantumtheory poses a serious problem for scientific realism, in that the theory is empirically extraordinarily successful, and yet has instrumentalism built into it. This paper stand this view on its head. I argue that orthodox quantumtheory suffers from a number of serious (if not always noticed) defects precisely because of its inbuilt instrumentalism. This defective character of orthdoox quantumtheory thus undermines instrumentalism, and (...) supports scientific realism. I go on to consider whether there is here the basis of a general argument against instrumentalism. (shrink)

QuantumTheory and the Flight from Realism is a critical introduction to the long-standing debate concerning the conceptual foundations of quantum mechanics, and the problems it has posed for physicists and philosophers from Einstein to the present. Quantumtheory has been a major influence on postmodernism, and presents significant challenges for realists. Clarifying these debates for the non-specialist, Christopher Norris examines the premises of orthodox quantumtheory and its impact on various philosophical developments. (...) He subjects a wide range of opponents and supporters of realism to a high and equal level of scrutiny. Combining rigor and intellectual generosity, he draws out the merits and weaknesses from opposing arguments. (shrink)

I propose a new class of interpretations, real world interpretations, of the quantumtheory of closed systems. These interpretations postulate a preferred factorization of Hilbert space and preferred projective measurements on one factor. They give a mathematical characterisation of the different possible worlds arising in an evolving closed quantum system, in which each possible world corresponds to a (generally mixed) evolving quantum state. In a realistic model, the states corresponding to different worlds should be expected (...) to tend towards orthogonality as different possible quasiclassical structures emerge or as measurement-like interactions produce different classical outcomes. However, as the worlds have a precise mathematical definition, real world interpretations need no definition of quasiclassicality, measurement, or other concepts whose imprecision is problematic in other interpretational approaches. It is natural to postulate that precisely one world is chosen randomly, using the natural probability distribution, as the world realised in Nature, and that this world’s mathematical characterisation is a complete description of reality. (shrink)

In order to claim that one has experimentally tested whether a noncontextual ontological model could underlie certain measurement statistics in quantumtheory, it is necessary to have a notion of noncontextuality that applies to unsharp measurements, i.e., those that can only be represented by positive operator-valued measures rather than projection-valued measures. This is because any realistic measurement necessarily has some nonvanishing amount of noise and therefore never achieves the ideal of sharpness. Assuming a generalized notion of noncontextuality (...) that applies to arbitrary experimental procedures, it is shown that the outcome of a measurement depends deterministically on the ontic state of the system being measured if and only if the measurement is sharp. Hence for every unsharp measurement, its outcome necessarily has an indeterministic dependence on the ontic state. We defend this proposal against alternatives. In particular, we demonstrate why considerations parallel to Fine’s theorem do not challenge this conclusion. (shrink)

This paper examines the epistemological significance of the present situation of underdetermination in quantum mechanics. After analyzing this underdetermination at three levels---formal, ontological, and methodological---the paper considers implications for a number of variants of the thesis of scientific realism in fundamental physics and reassesses Lakatos‘ characterization of progress in physical theory in light of the present situation. Next, this paper considers the implications of underdetermination for Weinberg’s ‘‘dream of a final theory.’’ Finally, the paper concludes by suggesting (...) how one might still think of realism and progress in fundamental physics despite the possibility of persistent underdetermination in quantum mechanics. (shrink)

It is argued that a realistic interpretation of quantum mechanics is possible and useful. Current interpretations, from “Copenhagen” to “many worlds” are critically revisited. The difficulties for intuitive models of quantum physics are pointed out and possible solutions proposed. In particular the existence of discrete states, the quantum jumps, the alleged lack of objective properties, measurement theory, the probabilistic character of quantum physics, the wave–particle duality and the Bell inequalities are analyzed. The sketch of (...) a realistic picture of the quantum world is presented. It rests upon the assumption that quantum mechanics is a stochastic theory whose randomness derives from the existence of vacuum fields. They correspond to the vacuum fluctuations of quantum field theory, but taken as real rather than virtual. (shrink)

Quantum Mechanics can be viewed as a linear dynamical theory having a familiar mathematical framework but a mysterious probabilistic interpretation, or as a probabilistic theory having a familiar interpretation but a mysterious formal framework. These points of view are usually taken to be somewhat in tension with one another. The first has generated a vast literature aiming at a “realistic” and “collapse-free” interpretation of quantum mechanics that will account for its statistical predictions. The second has (...) generated an at least equally large literature aiming to derive, or at any rate motivate, the formal structure of quantumtheory in probabilistically intelligible terms. In this paper I explore, in a preliminary way, the possibility that these two programmes have something to offer one another. In particular, I show that a version of the measurement problem occurs in essentially any non-classical probabilistic theory, and ask to what extent various interpretations of quantum mechanics continue to make sense in such a general setting. I make a start on answering this question in the case of a rudimentary version of the Everett interpretation. (shrink)

We put forward a possible new interpretation and explanatory framework for quantumtheory. The basic hypothesis underlying this new framework is that quantum particles are conceptual entities. More concretely, we propose that quantum particles interact with ordinary matter, nuclei, atoms, molecules, macroscopic material entities, measuring apparatuses, in a similar way to how human concepts interact with memory structures, human minds or artificial memories. We analyze the most characteristic aspects of quantumtheory, i.e. entanglement and (...) non-locality, interference and superposition, identity and individuality in the light of this new interpretation, and we put forward a specific explanation and understanding of these aspects. The basic hypothesis of our framework gives rise in a natural way to a Heisenberg uncertainty principle which introduces an understanding of the general situation of ‘the one and the many’ in quantum physics. A specific view on macro and micro different from the common one follows from the basic hypothesis and leads to an analysis of Schrödinger’s Cat paradox and the measurement problem different from the existing ones. We reflect about the influence of this new quantum interpretation and explanatory framework on the global nature and evolutionary aspects of the world and human worldviews, and point out potential explanations for specific situations, such as the generation problem in particle physics, the confinement of quarks and the existence of dark matter. (shrink)

Two successes of old quantumtheory are particularly notable: Bohr’s prediction of the spectral lines of ionised helium, and Sommerfeld’s prediction of the fine-structure of the hydrogen spectral lines. Many scientific realists would like to be able to explain these successes in terms of the truth or approximate truth of the assumptions which fuelled the relevant derivations. In this paper I argue that this will be difficult for the ionised helium success, and is almost certainly impossible for the (...) fine-structure success. Thus I submit that the case against the realist’s thesis that success is indicative of truth is marginally strengthened. (shrink)

A realistic axiomatic formulation of nonrelativistic quantum mechanics for a single microsystem with spin is presented, from which the most important theorems of the theory can be deduced. In comparison with previous formulations, the formal aspect has been improved by the use of certain mathematical theories, such as the theory of equipped spaces, and group theory. The standard formalism is naturally obtained from the latter, starting from a central primitive concept: the Galilei group.

After a brief account of theway quantumtheory deals with naturalprocesses, the crucial problem that such atheory meets, the measurement or, better, themacro-objectification problem is discussed.The embarrassing aspects of the occurrence ofentangled states involving macroscopic systemsare analyzed in details. The famous example ofSchroedinger's cat is presented and it ispointed out how the combined interplay of thesuperposition principle and the ensuingentanglement raises some serious difficultiesin working out a satisfactory quantum worldview, agreeing with our definiteperceptions. The orthodox solution to (...) themacro-objectification problem, i.e. thepostulate of wave packet reduction, isanalyzed and is proved to be inconsistent withthe assumption that the theory governes alsothe measurement process. After these premises,the rest of the paper is devoted to discuss arecent proposal of overcoming the difficultiesof the standard formalism by acceptingnonlinear and stochastic modifications of thequantum dynamics. The proposed theory is shownto agree with all known predictions of thestandard theory concerning microscopic systemsand to account, on the basis of a universaldynamics which is assumed to govern allnatural processes, for wave packet reductionin measurement processes and, more important,to eliminate all the difficulties concerningmacroscopic situations. Actually, the proposedtheory allows one to take consistently amacrorealistic position about natural processes and about our definite perceptions. (shrink)

Quantum theoretical developments in physical science challenge the foundational assumptions of both realist and constructivist social paradigms. Furthermore, when quantum metaphysics is coupled with biological, neuro-scientific discoveries that the brain regenerates and reprograms itself throughout life in response to environmental challenges and the force of attention and will, the result is a different picture of human nature and the social behavior that is possible, ethical, and scientifically plausible than that suggested by either social realists or constructivists. This article (...) explores the frontier of recent developments in the physical and biological sciences and considers how these findings might allow for a new foundation for social theory. (shrink)

Quantumtheory is a tremendously successful physical theory, but nevertheless suffers from two serious problems: the measurement problem and the problem of interpretational underdetermination. The latter, however, is largely overlooked as a genuine problem of its own. Both problems concern the doctrine of realism, but pull, quite curiously, into opposite directions. The measurement problem can be captured such that due to scientific realism about quantumtheory common sense anti-realism follows, while theory underdetermination usually counts (...) as an argument against scientific realism. I will also consider the more refined distinctions of ontic and epistemic realism and demonstrate that quantumtheory in its most viable interpretations conflicts with at least one of the various realism claims. A way out of the conundrum is to come to the bold conclusion that quantumtheory is, possibly, wrong (in the realist sense). (shrink)

The question raised by Shimony and Stein is examined and used to explain in more detail a key point of my proof that any theory that conforms to certain general ideas of orthodox relativistic quantum field theory must permit transfers of information over spacelike intervals. lt is also explained why this result is not a problem for relativistic quantumtheory, but, on the contrary, opens the door to a satisfactory realistic relativistic quantum (...) class='Hi'>theory based on the ideas of Tomonaga, Schwinger, and von Neumann. (shrink)

A method is proposed that should facilitate the construction of theories of “submicroscopic particles” (denoted as “theories of microchannels”) in a way similar to the use of group-theoretical methods. The “conceptual analysis” (CA) method is based on the analysis of the basic concepts of a theory; it permits a determination of necessary conditions imposed on the mathematical apparatus (of the theory) which then appear as a mathematical representation of the structures obtained in a formal scheme of a (...) class='Hi'>theory. A pertinent conceptual analysis leads to a new definition (“relativization”) of the concept “empirical implication.” The approach may be characterized as “realistic” and “operational.” The application of the CA method is illustrated on the example of quantumtheory. In Part I the algebraic structure of a partially ordered, up-ward directed, bounded set is deduced from the rudimentary concepts. In Parts II and III, we shall deduce the Hilbert-space structure (well established in quantum mechanics) from postulates on some essential idealizations accepted in the theory. Whereas Part II is concerned with the idealizations of existing quantum theories based on the Hilbert-space formalism, Part I may be considered as a general basis for a wider class of theories. (shrink)

Work on the central problems of the philosophy of science has led the author to attempt to create an intelligible version of quantumtheory. The basic idea is that probabilistic transitions occur when new stationary or particle states arise as a result of inelastic collisions.

[Abstract: Anti-realism – the denial that reality exists apart from our conceptions of it – is rampant, not just among Postmodernists and other literati, but also among many of the leading spokesmen of orthodox quantumtheory – from Born, Bohr, and Heisenberg to Wheeler and Wigner. Undoubtedly they've done good physics. Why, then, do they indulge in bad metaphysics? This paper offers some answers.].

Confused ideas about the weirdness of quantum mechanics have sometimes been blamed for the spread of anti-realist positions in philosophy. In this seminar, I shall re-examine the relation between realism and quantumtheory. My goal is to argue that one can remain a realist in a reasonably familiar sense, while adopting a theory which amounts to a form of idealism. After sketching the abstract mathematical structure of quantumtheory, I will introduce realism and consider (...) some of its problems and some counter-arguments. Next I will look at why quantumtheory needs an interpretation and at some of the features common to many proposed interpretations. Then I will discuss some of the gaps in decoherence theory, when it is considered as an interpretation of quantumtheory, and I will end with a sketch of my own realist version of idealism in which the fundamental entities are structures which define minds, and the fundamental laws govern the stochastic developments of those structures. (shrink)

The ambition of this book is a noble one: to provide a counter to the assumption, taken for granted made by many postmodernists, that quantum mechanics lends support to the view that scienti® c realism is nothing more than an outmoded fad. It is especially gratifying that this book comes from a literary theorist, author of a well-respected book on Derrida (Norris, 1987), who, by his own admission, has ª previously published several books on literary theory that might (...) be construed ¼ as going along with the emergent trend towards anti-realism and cultural relativism in various quarters of `advanced’ theoretical debateº (Introduction, p. 1). One wishes, however, that Norris had taken more time to familiarize himself with issues that he writes about, and that he had taken more care in constructing his arguments. Although ª there will be more joy in heaven over one sinner who repents than over ninety-nine righteous persons who need no repentanceº (Luke 15: 7, RSV), we should not let jubilation blind us to the book’ s shortcomings. Among these is a lack of clarity in its central notion, that of realism. Early on, Norris quotes with approval William Alston’ s characterization of the alethic conception of realism, which is the conception advocated by Norris; the alethic conception ª implies that (almost always) what confers a truth-value on a statement is something independent of the cognitive-linguistic goings-on that issued in that statement, including any epistemic status of those goings-onº (p. 41). As the book progresses, however, additional conditions on what is to count as a realist interpretation of quantum mechanics emerge. Realism apparently becomes synonymous with ª causal-explanatoryº theories, and in one passage, Norris goes so far as to suggest that realism entails a commitment to synthetic a priori knowledge of the physical world: Bell’ s calculations and those applied in interpreting the Aspect results are themselves dependentÐ no less than EPRÐ on a range of distinctly ª classicalº assumptions, among them the existence of a physical object-domain which, however puzzling its details, permits such experiments to be carried out and conclusions to be drawn from them.. (shrink)

Based on the new general framework for the probabilistic description of experiments, introduced in [E.R. Loubenets, Research Report No 8, MaPhySto, University of Aarhus, Denmark (2003); Proceedings Conference “QuantumTheory, Reconsideration of Foundations”, Ser. Math. Modeling, Vol. 10 (University Press, Vaxjo, 2004), pp. 365–385], we analyze in mathematical terms the link between the validity of Bell-type inequalities under joint experiments upon a system of any type and the physical concept of “local realism”. We prove that the violation of (...) Bell-type inequalities in the quantum case has no connection with the violation of “local realism”. In a general setting, we formulate in mathematical terms the condition on “local realism” under a joint experiment and consider examples of quantum “locally realistic” joint experiments. We, in particular, show that quantum joint experiments of the Alice/Bob type are “locally realistic”. For an arbitrary bipartite quantum state, we derive quantum analogs of the original Bell inequality. In view of our results, we argue that the violation of Bell-type inequalities in the quantum case cannot be a valid argument in the discussion on locality or non-locality of quantum interactions. (shrink)

In this paper I put forward a suggestion for identifying causality in micro-systems with the specific quantum field theoretic interactions that occur in such systems. I first argue — along the lines of general transference theories — that such a physicalistic account is essential to an understanding of causation; I then proceed to sketch the concept of interaction as it occurs in quantum field theory and I do so from both a formal and an informal point (...) of view. Finally, I present reasons for thinking that only a quantum field theoretic account can do the job — in particular I rely on a theorem by D. Currie and to the effect that interaction cannot be described in (a Hamiltonian formulation of) Classical Mechanics. Throughout the paper I attempt to suggest that the widespread scepticism about the ability of quantumtheory to support a theory of causality is mistaken and rests on several misunderstandings. (shrink)

It is widely held that quantum mechanics is the first scientific theory to present scientifically internal, fundamental difficulties for a realistic interpretation (in the philosophical sense). The standard (Copenhagen) interpretation of the quantumtheory is often described as the inevitable instrumentalistic response. It is the purpose of the present article to argue that quantumtheory doesnot present fundamental new problems to a realistic interpretation. The formalism of quantumtheory has the (...) same states—it will be argued—as the formalisms of older physical theories and is capable of the same kinds of philosophical interpretation. This result is reached via an analysis of what it means to give a realistic interpretation to a theory. The main point of difference between quantum mechanics and other theories—as far as the possibilities of interpretation are concerned—is the special treatment given tomeasurement by the “projection postulate.” But it is possible to do without this postulate. Moreover, rejection of the projection postulate does not, in spite of what is often maintained in the literature, automatically lead to the many-worlds interpretation of quantum mechanics. A realistic interpretation is possible in which only the reality ofone (our) world is recognized. It is argued that the Copenhagen interpretation as expounded by Bohr is not in conflict with the here proposed realistic interpretation of quantumtheory. (shrink)

1. Realism. Physicists claim rightly to speak about reality. But what does “reality” mean?2. The Copenhagen Interpretation (CI). We consider CI as a minimal semantics for quantumtheory, leaving ways open for additional interpretation.3. The Measuring Process. Several interpretations of the process as given in the liteature are discussed.4. Realistic Interpretation. Discussion of the de Broglie-Bohm-Bell interpretation. If well formulated, it is not a necessary consequence of quantumtheory but cannot be excluded.

The basic theme of Popper's philosophy--that something can come from nothing--is related to the present situation in physical theory. Popper carries his investigation right to the center of current debate in quantum physics. He proposes an interpretation of physics--and indeed an entire cosmology--which is realist, conjectural, deductivist and objectivist, anti-positivist, and anti-instrumentalist. He stresses understanding, reminding us that our ignorance grows faster than our conjectural knowledge.

The axiomatic approaches of quantum mechanics and relativity theory are compared with approaches in which the theories are thought to describe readings of certain measurement operations. The usual axioms are shown to correspond with classes of ideal measurements. The necessity is discussed of generalizing the formalisms of both quantum mechanics and relativity theory so as to encompass more realistic nonideal measurements. It is argued that this generalization favours an empiricist interpretation of the mathematical formalisms over (...) a realist one. (shrink)

Recent suggestions to supply quantum mechanics (QM) with realistic foundations by reformulating it in light of quantum information theory (QIT) are examined and are found wanting by pointing to a basic conceptual problem that QIT itself ignores, namely, the measurement problem. Since one cannot ignore the measurement problem and at the same time pretend to be a realist, as they stand, the suggestions to reformulate QM in light of QIT are nothing but instrumentalism in disguise.

The axiomatic approaches of quantum mechanics and relativity theory are compared with approaches in which the theories are thought to describe readings of certain measurement operations. The usual axioms are shown to correspond with classes of ideal measurements. The necessity is discussed of generalizing the formalisms of both quantum mechanics and relativity theory so as to encompass more realistic nonideal measurements. It is argued that this generalization favours an empiricist interpretation of the mathematical formalisms over (...) a realist one. (shrink)

A realistic physical axiomatic approach of the relativistic quantum field theory is presented. Following the action principle of Schwinger, a covariant and general formulation is obtained. The correspondence principle is not invoked and the commutation relations are not postulated but deduced. The most important theorems such as spin-statistics, and CPT are proved. The theory is constructed form the notion of basic field and system of basic fields. In comparison with others formulations, in our realistic approach (...) fields are regarded as real things with symmetry properties. Finally, the general structure is contrasted with other formulations. (shrink)

D. Dieks has proposed a semantical rule which he claims yields a realistic interpretation of the formalism of quantum mechanics without the projection postulate. I argue that his proposal is unacceptable because it violates a natural requirement of psychophysical parallelism. His "semantical rule" is not an acceptable interpretive rule because it does not identify structures in the theory with structures in our experience, but postulates a merely probabilistic relationship between the two. Dieks' interpretation is contrasted with Everett's (...) relative state interpretation, which attempts the same task but respects psychophysical parallelism. (shrink)

In this paper I outline my propensiton version of quantumtheory (PQT). PQT is a fully micro-realistic version of quantumtheory that provides us with a very natural possible solution to the fundamental wave/particle problem, and is free of the severe defects of orthodox quantumtheory (OQT) as a result. PQT makes sense of the quantum world. PQT recovers all the empirical success of OQT and is, furthermore, empirically testable (although not (...) as yet tested). I argue that Einstein almost put forward this version of quantumtheory in 1916/17 in his papers on spontaneous and induced radiative transitions, but retreated from doing so because he disliked the probabilistic character of the idea. Subsequently, the idea was overlooked because debates about quantumtheory polarised into the Bohr/Heisenberg camp, which argued for the abandonment of realism and determinism, and the Einstein/Schrödinger camp, which argued for the retention of realism and determinism, no one, as a result, pursuing the most obvious option of retaining realism but abandoning determinism. It is this third, overlooked option that leads to PQT. PQT has implications for quantum field theory, the standard model, string theory, and cosmology. The really important point, however, is that it is experimentally testable. I indicate two experiments in principle capable of deciding between PQT and OQT. (shrink)

What sort of entities are electrons, photons and atoms given their wave-like and particle-like properties? Is nature fundamentally deterministic or probabilistic? Orthodox quantumtheory (OQT) evades answering these two basic questions by being a theory about the results of performing measurements on quantum systems. But this evasion results in OQT being a seriously defective theory. A rival, somewhat ignored strategy is to conjecture that the quantum domain is fundamentally probabilistic. This means quantum entities, (...) interacting with one another probabilistically, must differ radically from the entities of deterministic classical physics, the classical wave or particle. It becomes possible to conceive of quantum entities as a new kind of fundamentally probabilistic entity, the “propensiton”, neither wave nor particle. A fully microrealistic, testable rival to OQT results. (shrink)

Specker contradiction, I prove that ‘local realistic’ theories predict nontrivial violations of the quantum mechanical EPR-type perfect anticorrelations. The proof invokes the same stochastic local realism conditions used in Bell arguments. For a class of theories called ‘orthodox spin theories’, the perfect anticorrelations used in the proof emerge from rotational symmetry. Therefore, an orthodox spin theorist must abandon either the spirit of relativity, as encoded by local realism, or the letter of relativity, which demands rotational invariance.

In response to Cushing it is urged that the vicissitudes of quantum field theory do not press towards a nonrealist attitude towards the theory as strongly as he suggests. A variety of issues which Redhead raises are taken up, including photon localizability, the wave-particle distinction in the classical limit, and the interpretation of quantum statistics, vacuum fluctuations, virtual particles, and creation and annihilation operators. It is urged that quantum field theory harbors an unacknowledged inconsistency (...) connected with the fact that the zero point energy has observable consequences, while to avoid infinities it must be "thrown away". Finally, Redhead's conception of ephemerals is pressed and the paper concludes with the suggestion that the particle concept largely drops out of quantum field theory. (shrink)

Sorkin’s recent proposal for a realist interpretation of quantumtheory, the anhomomorphic logic or coevent approach, is based on the idea of a “quantum measure” on the space of histories. This is a generalisation of the classical measure to one which admits pair-wise interference and satisfies a modified version of the Kolmogorov probability sum rule. In standard measure theory the measure on the base set Ω is normalised to one, which encodes the statement that “Ω happens”. (...) Moreover, the Kolmogorov sum rule implies that the measure of any subset A is strictly positive if and only if A cannot be covered by a countable collection of subsets of zero measure. In quantum measure theory on the other hand, simple examples suffice to demonstrate that this is no longer true. We propose an appropriate generalisation, the quantum cover, which in addition to being a cover of A, satisfies the property that if the quantum measure of A is non-zero then this is also the case for at least one of the elements in the cover. Our work implies a non-triviality result for the coevent interpretation for Ω of finite cardinality, and allows us to cast the Peres-Kochen-Specker theorem in terms of quantum covers. (shrink)

The relation between micro-objects and macro-objects advocated by Kim is even more problematic than Ross & Spurrett (R&S) argue, for reasons rooted in physics. R&S's own ontological proposals are much more satisfactory from a physicist's viewpoint but may still be problematic. A satisfactory theory of macroscopic ontology must be as independent as possible of the details of microscopic physics.

Recent advantages in experimental quantum physics call for a careful reconsideration of the measurement process in quantum mechanics. In this paper we describe the structure of the ideal measurements and their status among the repeatable measurements. Then we provide an exhaustive account of the interrelations between repeatability and the apparently weaker notions of value reproducible or first- kind measurements. We demonstrate the close link between repeatable measurements and discrete observables and show how the ensuing measurement limitations for continuous (...) observables can be lifted in a way that is in full accordance with actual experimental practice. We present examples of almost repeatable measurements of continuous observables and some realistic models of weakly disturbing measurements. (shrink)

As previous Växjö conferences on quantum foundations, QTRF-5 was notable not only for the contributions of the papers presented there but also for its exciting debates. These debates offered a great diversity of opinions on foundations of quantum mechanics (QM) and its future developments: from those defined by the view of those who adhere to the orthodox Copenhagen interpretation (which rejected realism and causality), at one end of the spectrum, to those who subscribed to realist views of the (...) type advocated by Einstein, at the other end, with a number of views in between. (shrink)